1. Field of the Invention
This invention relates to a foldable bicycle, more particularly to a foldable bicycle with four linking joints for folding and unfolding the bicycle without the need to detach any component parts therefrom.
2. Description of the Related Art
Referring to FIGS. 1 and 2, in a Taiwanese publication No. M265307, entitled “Rapidly and Easily Foldable Bicycle,” there is disclosed a foldable bicycle 1 which includes a head tube 11, a bottom tube 12, a seat tube 13, a saddle 14, a locking device 15, front and rear wheels 161,162, and a transmitting device 17. The bottom tube 12 has one end pivoted to the head tube 11 at a first pivot point 121. The seat tube 13 has an end pivoted to the head tube 11 at a second pivot point 131, and an opposite end pivoted to the other end of the bottom tube 12 at a third pivot point 132. The saddle 14 is mounted on the seat tube 13 away from the head tube 11. The locking device 15 includes a sleeve 151 sleeved on the head tube 11, and a quick-release fastener 152 disposed to fasten the sleeve 151 to the head tube 11. The front and rear wheels 161,162 are pivotally mounted on two end extensions of the bottom tube 12. The transmitting device 17 is mounted on the bottom tube 12 to drive the rear wheel 162 so as to generate rotation of the wheels 161,162.
When it is desired to fold the bicycle 1, the fastener 152 is released so as to permit movement of the first pivot point 121 along the head tube 11. The head tube 11, the bottom tube 12 and the seat tube 13 can be folded by virtue of the second and third pivot points 131,132. However, it is difficult to move the bottom tube 12 along the head tube 11 smoothly due to change of the pivot angle therebetween during the folding operation, thereby resulting in inconvenient to the operator. Moreover, since the front and rear wheels 161,162 have the same wheel radius, they have to be relatively turned so as not to interfere with each other. Thus, the front and rear wheels 161,162 can not be maintained in tandem after folding to enable the folded bicycle to be pushed along, thereby resulting in inconvenience during transport of the bicycle 1.